TUGAS KIMIA UMUM C (kelompok jadual kuliah Kamis Pagi jam 08.00) 1. The radii of the sodium and potassium ions are 102 pm and 138 pm, respectively. Which compound has stronger ionic attractions, sodium chloride or potassium chloride? 2. Does potassium nitrate (KNO3) incorporate ionic bonding, covalent bonding, or both? Explain. 3. An X-ray has a wavelength of 1.3 Å. Calculate the energy (in Joule) of one photon of this radiation. 4. The following quantum number combinations are not allowed. Assuming the n and ml values are correct, change the l value to create an allowable combination: (a). n=3, l=0, ml=-1; (b). n=3, l=3, ml=+1; (c). n=7, l=2, ml=+3; (d). n=4, l=1, ml=-2. 5. Write a full set of quantum numbers for the following: (a). outermost electron in an Rb atom; (b). The electron gained when an S- ion becomes an S2- ion; (c). The electron lost when an Ag atom ionizes; (d). the electron gained when an F - ion forms from an F atom 6. Palladium (Pd, Z=46) is diamagnetic. Draw partial orbital diagram to show which of the following electron configurations is consistent with this fact: (a). [Kr]5s 2 4d8; (b) [Kr]4d10; (c). [Kr]5s1 4d9 7. Both nitrogen and bismuth are members of Groups 5A(15). Which is more metallic? Explain your answer in term of atomic properties. 8. When liquid benzene (C6H6) boils, does the gas consists of molecules, ions, or separate atoms? Explain scientifically.
Petunjuk: 1. Kerjakan tugas kuliah ini dengan menjawab masing-masing pertanyaan 2. Jawaban pertanyaan harus diketik di pengolah kata (MS Word atau Open Office) kemudian harus dionlinekan di masing-masing blog mahasiswa dalam bentuk file PDF. 3. Jawaban Tugas ini harus sudah dionlinekan di weblog Anda paling lambat tanggal 24 Oktober 2010 jam 23.00 WIB. 4. Jika pada tanggal tersebut (no. 3) belum online di masing-masing weblog, maka dianggap mahasiswa yang bersangkutan tidak mengumpulkan tugas. 5. Tuliskan identitas anda di jawaban anda. 6. Tuliskan identitas blog anda di jawaban anda
7. Bagi kelompok kuliah yang belum mengumpulkan daftar blog, silakan segera mengumpulkan daftar blog. 8. Sumber literature boleh dari mana saja, yang penting sumber literature disebutkan dengan jelas.
Name : Maylia Selvi Suswadi Class : A NIM : 21030110110049 Web : selvieesh.wordpress.com
Answers 1. Sodium chloride. Because sodium chloride has less diameter. The ionic bonding is conditional with the power of attraction. And the ionic attraction is written as the Coulomb Law: “Energy of attraction or repulsion between two particles is proportional to the product of their charges and unproportional to the distance. “ In short, the Coulomb Law is Energy
ch arg e1 ch arg e2 dis tan ce
Thus, ions with less distance areore attractive because they are closer.
Cl-
Na+ 102
Cl-
K+ 138
2. Potassium Nitrate has both ionic and covalent bonds because it is polyatomic. The ionic bonding is between K and NO3 and the covalent bonding is the NO3 .
3. 1,3 Å 1,3 10 10 m
E hv h E
c
6,626 10
34
Js 3 108 m / s 1,3 10 10 m
E 15,3 10 16 J
4. (a) n=3 ; l=0 ; ml=-1 3s doesn’t have -1 magnetic quantum number, so to make it valid, l=1 or l=2 (b) n=3 ; l=3 ; ml=+1 When n=3, there’s no f sublevel. So, l=1 or l=2 (c) n=7 ; l=2 ; ml = +3 When n=7, the only sublevels are s and p. So, l=0 and ml=0 or ml=1 (d) n=4 ; l=1 ; ml=-2 4p doesn’t have -2 quantum number, so to make it valid, l=2 or l=3
5. A.
37
Rb e=37
[Kr] 5s 1 n=5 ; l=0 ; ml=0 ; ms=-1/2 B.
16
S 2 e=18
[Ne] 3s 2 3p 6 n=3 ; l=1 ; ml=1 ; ms=-1/2 C. AgAg +e 47
Ag e=46
[Kr]4d 10 5s 1 n=5 ; l=0 ; ml=0 ; ms=+1/2 D. F e=10 1s 2 2s 2 2p 6 n=2 ; l=1 ; ml=1 ; ms=-1/2
6. A.
46
Pd: [Kr] 5s 2 3d 8
Paramagnetic
B.
46
Pd: [Kr] 4d 10 5s 0
Diamagnetic
C.
46
Pd: [Kr] 5s 1 3d 9
Paramagnetic
So, the correct answer is
46
Pd: [Kr] 4d 10 5s 0 because its configuration is
diamagnetic. 7. Nitrogen and Bismuth are both in Group VA. But, Bismuth is in Period 6 and Nitrogen is in Period 2. In a group, the radius from up downward is increasing, thus the radius of Bismuth is bigger and the ionization energy is smaller and easier to lose electrons. Metals are easy to lose electrons. Therefore, Bismuth is more metallic than Nitrogen.
8. Molecules. Benzene is a stable compound. Why? Look at the configuration below.
The dipole forces in benzene are stable. The charges are balanced. The electronegativity of C is 2.6 and the electronegativity of H is 2.2. Therefore, C atoms attract the electrons and the electrons are closer to C. But, as we can see, benzene is hexahedral and that’s why the intermolecule dipole forces are high. Thus, benzene is hard to be separated. This makes benzene evaporates as molecules.
REFERENCES: Istadi, Aprilina Purbasari. 2008. Buku Ajar Kimia Umum Jurusan Teknik Kimia Fakultas Teknik Universitas Diponegoro Semarang http://www.meta-synthesis.com/webbook/30_timeline/timeline.html http://csrchem2005.bootsglobal.com/main.asp?pid=684 http://en.wikipedia.org/wiki/Potassium_nitrate
